Question

The image of an object placed 30cm from a diverging lens is formed 10cm in front of the lens.

Calculate the focal length of the lens.​

Answer 1

15cm

Step-by-step explanation:

Since the lens is a diverging lens, the image distance is negative (virtual)

v = -30cm

u = 10cm

Required

focal length f

Using the lens formula;

1/u + 1/v = 1/u

1/10 - 1/30 = 1/f

(3-1)/30 = 1/f

2/30 = 1/f

f = 30/2

f = 15cm

Hence the focal length of the lens is 15cm